Studies On The Mechanism Of PCD Of Elm Seeds During Accelerated Aging

Elm seeds were used to investigate characters of programmed cell death(PCD) after aging for 6 days at 37℃and 100%relative humidity(RH) in this article.TUNEL-positive results indicating the occurrence of DNA strand breaks were detected in some of the cotyledon and embryonic axis cells,while the TUNEL-positive nuclei increased with increasing accelerated ageing time,which gave antoher evidence to PCD of elm seeds during accelerated aging.Water content of elm seeds gradually increased,while the respiration rate peaked at the 3.5 days of accelerated ageing,and then decreased.The production and scavenging of reactive oxygen species(ROS) became imbalanced and there was an immediate oxidative burst.Furthermore,the increased generation of H₂O₂ caused mitochondrial disorganization, the opening of the mitochondrial permeability transition(MPT) and the loss of mitochondrial transmembrane potential(△ψm),which in turn caused cytochrome c(Cyt c) release from mitochondria--a known mitochondrial hallmark in plant PCD.These evidences suggested that ROS was involved in triggering cell death during the accelerated aging and this reaction was induced via a mitochondrial pathway,even though the mechanism underlying this process is largely speculative and needs to be further corroborated.